For example, a metal and a semiconductor such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, or stainless steel, and an alloy thereof; a glassy substance such as quartz glass, aluminosilicate glass, or glassy carbon; a ceramic material such as alumina, silica, sapphire, silicon nitride, tantalum nitride, or titanium carbide; a compound semiconductor wafer material such as silicon carbide, gallium nitride, or gallium arsenide; and a resin material such as a polyimide resin are polished according to various requests such as flattening, and are applied in various fields.
Above all, in order to produce a semiconductor device such as an integrated circuit, various studies on a technique for polishing a silicon wafer have been performed to produce a mirror wafer having a high-quality flat mirror surface without scratches or impurities.
A polishing step of a semiconductor wafer such as a silicon wafer may be performed by at least two stages of preliminary polishing and final polishing. In the preliminary polishing, rough polishing is performed in order to flatten a surface or improve surface roughness. The final polishing is performed in order to improve haze (cloudiness) or remove polishing defects.
In such multi-stage polishing, Patent Literature 1 focuses on the following point. That is, when a subsequent polishing step is performed while abrasive grains in a polishing composition used in a preceding polishing step remain on a wafer surface after completion of polishing, in the subsequent polishing step, defects caused by polishing, such as scratches, are generated on the wafer surface due to the remaining abrasive grains. Patent Literature 1 discloses a polishing composition in which (1) the particle diameter of abrasive grains included (polishing abrasive grains before a final step) is equal to or more than that of abrasive grains in a polishing composition used in a polishing step two stages before the final step (polishing abrasive grains two stages before final step) and (2) the concentration of the polishing abrasive grains before the final step is equal to or less than that of polishing abrasive grains two stages before the final step in a polishing composition used in the polishing step two stages before the final step. Patent Literature 1 discloses a technique to obtain a semiconductor wafer having a high quality of surface, which can be adapted to a highly integrated device.
Haze generated on the surface of the semiconductor wafer during wafer processing not only affects electrical characteristics and a yield of the semiconductor device but also reduces a detection limit when particles adhering to the wafer surface are measured by a particle counter. A haze level of the surface of the semiconductor wafer obtained by a producing method by precisely polishing the surface using a conventional polishing composition is becoming insufficient because in the present, the quality required for the semiconductor wafer is becoming more severe due to the high performance and high integration density of the semiconductor device. According to more detailed semiconductor device design rules, similarly, LLS (Localized Light Scatters) which are a kind of defects observed on the wafer surface after polishing is performed using a polishing composition, are required to have a higher quality because the LLS affect the performance of the semiconductor device.
In this point, even when polishing is performed using the polishing method disclosed in Patent Literature 1, an amount of haze cannot be reduced, and defects cannot be removed sufficiently.